I am looking for a dark set of clothes, non armor rated gear to match a stealth vampiric assassin. Any ideas as to where to find some of this? preferably non enchanted. Looking for hood and robes and footwear. Any ideas to a location, maybe the cloth shop in solitude though I have gone searching yet.

Necromancer robes / black mage robes, Dark Brotherhood cowls are good, either fortify sneak or archery, and Dark Brotherhood shrouded shoes have muffle and look like normal shoes.

Can those be enchanted? I have the double enchanting perk if that matters.

Black Mage Robes has no enchantment, so yeah. I have no idea about DB gear, I do know they aren't disenchantable without mods. Necromancer robes should work.

You can come across unenchanted black robes and probably hooded black robes. Maybe some unenchanted necromancer robes, not sure if they'll be hooded though. Worn Dark Brotherhood cowls will be unenchanted, but they'll probably be armor only for the unenchanted stuff.

Mourner's Clothes and Mourner's Hat are sold at Radiant Raiment. I think there's probably a male and female model for the clothes. They are plain and dark, so good for not getting the wrong kind of attention.

This.

FWIW the hat doesn't cover the face, but you could probably get an Executioner's Hood somewhere. Of course it covers the eyes, but there are very few headpieces that cover the face.